For user verification and other purposes, many devices such as portable computers and cellular telephone include a fingerprint sensor. A fingerprint sensor, sometimes called a biometric sensor, senses a fingerprint of a finger place on the fingerprint sensor. The obtained fingerprint is compared to an authorized user's stored fingerprint. If there is a match, the user is verified.
There are two commonly used fingerprint sensors in consumer applications. The first type of fingerprint sensor is a silicon die fingerprint sensor. The sensing element that senses the fingerprint is located on an active surface of the silicon die fingerprint sensor.
The second type of fingerprint sensor is a sensing element on flex fingerprint sensor. The sensing element that senses the fingerprint is located on a flexible dielectric substrate.
To reduce the cost of the devices in which the fingerprint sensors are used, it is desirable to package the fingerprint sensors at low cost.
In the following description, the same or similar elements are labeled with the same or similar reference numbers.